Please add to documentation (README) what standard AWS variables are supported.

I discovered by accident that profile name does not have to be a part of codedommit URL, but instead can be obtained from `AWS_PROFILE` environment variable.

While this is not a preferred way of setting up your local environment, it is absolutely necessary for automation, e.g. modules in Terraform.

Where you don't want to hardcode profiles in morule's source URL, but can setup a profile on the side and use it to get access to the repo when initializing your terraform.

I.e.
```
module "my_module" {
source = "git::codecommit::us-east-1://my-module-repo?ref=main"
...
}
```
I can then run my terraform like this:
```
AWS_PROFILE=my-profile terraform init
```